FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Foram objetivos deste estudo, (i) conhecer as concentraÃÃes hormonais de leptina e insulina em ovelhas, bem como verificar o efeito do escore de condiÃÃo corporal (ECC), do grupo genÃtico e da suplementaÃÃo sobre as concentraÃÃes de leptina, insulina e glicose mensuradas durante a estaÃÃo de monta, e ainda estudar as associaÃÃes entre estes efeitos e os metabÃlitos sanguÃneos em ovelhas vazias; (ii) avaliar a influÃncia dos efeitos da classe de condiÃÃo corporal, idade, semana de coleta, grupo genÃtico e da suplementaÃÃo energÃtica fornecida antes e durante a estaÃÃo de monta, sobre o peso e a condiÃÃo corporal das fÃmeas, e a influÃncia destes efeitos sobre os parÃmetros reprodutivos, taxa de gestaÃÃo, fertilidade e prolificidade; (iii) e ainda, avaliar os efeitos que exercem influÃncia sobre o peso da ovelha ao parto, o peso da cria ao nascer e sobre a produtividade total das ovelhas do rebanho, traduzida no presente estudo em quilos de cordeiro produzido por fÃmea parida. O experimento foi conduzido na Fazenda Experimental Vale do AcaraÃ, situada no municÃpio de Sobral â CearÃ. As ovelhas foram divididas em dois grupos segundo o grupo genÃtico e o tratamento: Santa InÃs com ou sem suplementaÃÃo (24x24) e Morada Nova com ou sem suplementaÃÃo (24x24), totalizando 96 ovelhas. Todas as fÃmeas foram manejadas em piquetes com mineralizaÃÃo e Ãgua ad libitum, porÃm o grupo 1 (controle) de cada tratamento nÃo foi suplementado e o grupo 2 recebeu suplementaÃÃo. Foram realizadas semanalmente coletas de sangue e informaÃÃes referentes ao peso e ECC das ovelhas. Os dados foram submetidos à ANOVA para se avaliar o efeito da classe de ECC, grupo genÃtico e suplementaÃÃo (lote), sobre o peso corporal, concentraÃÃes de glicose e concentraÃÃes de leptina e insulina, peso e a produtividade das ovelhas. Os parÃmetros reprodutivos como, taxa de gestaÃÃo, fertilidade e prolificidade foram comparados pelo teste de c 2 com 5% de probabilidade de erro. Foram estimadas as correlaÃÃes simples de Pearson entre as concentraÃÃes hormonais, peso e condiÃÃo corporal em funÃÃo do grupo genÃtico e tratamento. Constatou-se que a leptina està presente em baixas concentraÃÃes em ovelhas deslanadas e nÃo influenciando os processos reprodutivos destes animais sob essas condiÃÃes de criaÃÃo. A insulina mostrou importantes associaÃÃes com as variÃveis estudadas, podendo ser indicativa da condiÃÃo nutricional das ovelhas em estaÃÃo de monta. A suplementaÃÃo energÃtica promoveu o aumento do peso e melhorou o escore de condiÃÃo corporal das fÃmeas, nÃo refletindo, contudo, sobre os parÃmetros reprodutivos das ovelhas. O peso corporal das fÃmeas à pariÃÃo à influenciado pelo grupo genÃtico e idade da ovelha. Jà o peso ao nascer dos cordeiros pode ser influenciado pelo tipo de nascimento, peso da ovelha à pariÃÃo e pelo sexo da cria. O escore de condiÃÃo corporal, o genÃtipo e o tipo de nascimento influenciam na produtividade em quilos de cordeiro por ovelha parida. Entretanto, o fornecimento de suplementaÃÃo durante a estaÃÃo de monta nÃo resultou no aumento da produtividade em quilo de cordeiro produzido por ovelha parida no rebanho. Diante do exposto, conclui-se que o fornecimento de suplementaÃÃo energÃtica, para ovelhas deslanadas criadas na regiÃo semiÃrida do nordeste brasileiro, quando manejadas em sistema de pastejo rotacionado recebendo mineralizaÃÃo e Ãgua ad libitum pode ser dispensada, uma vez que a sua oferta onerou os custos de produÃÃo e nÃo resultou em aumento significativo na produtividade das ovelhas. / Through this study it is aimed, (i) to know the leptin and insulin concentrations in sheep, as well as to verify the effect of body condition score (BCS), breed and supplementation on the leptin, insulin and glucose concentrations measured during the breeding season, and also to study the associations between these effects and blood metabolites in empty sheep (ii) to evaluate the influence of class effects of body condition, age, collection week, breed and energy supplementation provided before and during the breeding season, on female weight and body condition, and the influence of these effects on reproductive parameters, pregnancy rate, fertility and prolificity; (iii)and also to evaluate the effects which influence the ewe weight at lambing, the offspring weight at birth and on the total productivity of the flock, referred to in the present study in pounds of lamb produced per female lambing. The experiment was conducted at the Experimental Farm Acaraà Valley, located in the municipality of Sobral - CearÃ. The sheep were divided into two groups according to breed and treatment: Santa InÃs, with or without supplementation (24x24) and Morada Nova with or without supplementation (24x24), totalizing 96 sheep. All ewes grazed in paddocks with mineralization and water ad libitum, however group 1 (control) of each treatment was not supplemented and group 2 received supplementation. Blood samplesand information relating to sheep weight and BCS were collected weekly during the breeding season. Data were submitted to ANOVA to evaluate the effect of the BCS class, breed and supplementation (lot), on body weight, glucose levels and leptin and insulin concentrations, ewe weight and sheep productivity The ewe reproductive parameters, pregnancy rate, fertility and prolificity were compared with test having 5% of error probability. Pearson correlation were estimated among hormone concentrations, weight and body condition related to breed and treatment. It was concluded that leptin is present in low concentrations in hair seep sheep and it seems not to influence the reproductive processes of those animals raised under these conditions. Insulin showed significant associations with the variables studied, which may be indicative of nutritional status of ewes in the breeding season. Energy supplementation promoted weight gain and improved body condition score of females. However, its effect was not reflected on the ewe reproductive parameters. The body weight of females at parturition is influenced by ewe breed and age. The lamb birth weight can be influenced by the type of birth, ewe weight at lambing and sex of the offspring. The body condition score, breed and type of birth influence productivity in kilograms of lamb per ewe parity. However, the supply of supplementation during the breeding season did not result in increased productivity per kilogram of lamb produced per female lambing. According to what was exposed above, it can be concluded that the supply of energy supplementation for hair seep ewes raised in the semi-arid region of Northeastern Brazil, raised under rotational grazing and receiving mineralization and water ad libitum, resulted in no significant increase in sheep productivity and can, therefore, be waived.

A presente tese foi dividida em 5 Experimentos. Os objetivos do Experimento 1 foram avaliar a utilização da gonadotrofina coriônica equina (eCG) e/ou do cipionato de estradiol (ECP) na dinâmica folicular e taxa de concepção de vacas holandesas submetidas a inseminação em tempo fixo (IATF). No D0, todos os animais (n = 782) receberam 2 mg de benzoato de estradiol (BE) e um dispositivo intravaginal de progesterona (CIDR). Oito dias depois, o CIDR foi retirado e todos os animais receberam PGF2?. Simultaneamente, os animais foram divididos em 4 grupos: G1) eCG + ECP no Dia 8; G2) eCG no Dia 8 + GnRH após 48h; G3) ECP no Dia 8; G4) GnRH após 48h. Amostras de sangue e exames utlra-sonográficos foram realizados frequentemente em um subgrupo de animais (n = 96). As análises estatísticas de todos os experimentos foram efetuadas com o proc GLIMMIX e proc MIXED do SAS. O uso de eCG e o escore de condição corporal (ECC) dos animais afetaram as concentrações circulantes de progesterona no diestro. Os animais do G2 apresentaram maior taxa de concepção que os do G4 (33,8% vs. 28,9%). Além disso, para animais de menor ECC, ficou evidente o benefício da aplicação de eCG (G2 = 44,4% vs. G4 = 6,1%). No Experimento 2 (n = 26), o objetivo foi comparar o efeito da administração da eCG no dia da remoção do CIDR em animais de menor (2,0-2,5) ou maior (3,0-3,5) ECC. Foram avaliadas algumas características do corpo lúteo (CL) como o volume e histologia, assim como as concentrações plasmáticas de progesterona no diestro. Independentemente da condição corporal dos animais, a eCG aumentou o volume do CL e a concentração plasmática de progesterona no diestro. O ECC afetou negativamente o volume e concentração de progesterona sérica no diestro. Não foi encontrado diferença na proporção de células grandes/pequenas, assim como no fluxo sanguíneo no CL entre os grupos experimentais. No Experimento 3, foi comparado a taxa de concepção em vacas de leite de alta produção (n = 388) após o uso do protocolo G2 do Experimento 1 (Capítulo I), com ou sem adição de ECP no momento da retirada do CIDR (novo ou usado). Não foi verificado efeito da adição do tratamento com ECP e nem do tipo do dispostivo na taxa de concepção. No Experimento 4 (n = 199), apesar no aumento verificado no diâmetro folicular no grupo tratado com GnRH 56h (17,8 mm) comparado com GnRH 48h (16,5 mm); e do atraso no momento da ovulação após a retirada do CIDR (GnRH 56h = 75,3h; GnRH 48h = 79,8h) não foi constatado qualquer diferença na concepção ao se atrasar a aplicação do GnRH de 48h para 56h em vacas inseminadas 16h depois do GnRH. No Experimento 5 (n = 185), a taxa de concepção não diferiu em animais que receberam o GnRH 48h ou 56h (momento da IATF) após a retirada do CIDR, indicando a possibilidade do emprego de um protocolo com apenas 3 manejos em vacas de leite de alta produção. / The current thesys has been divided in 5 Experiments. Objectives of Experiment 1 were to evaluate the effects of equine chorionic gonadotropin (eCG) and/or estradiol cypionate (ECP) on follicular dymanics and conception rate in Holstein cows receiving fixed timed artificial insemination (TAI). On D0, all cows (n = 782) received 2 mg of estradiol benzoate (EB) and one intravaginal progesterone device (CIDR). Eight days later, CIDR was removed and all animals were treated with PGF2?. Simultaneously, animals were divided in 4 groups: G1) eCG + ECP on Day 8; G2) eCG on Day 8 + GnRH 48h later; G3) ECP on Day 8; G4) GnRH 48h later. Blood samples and ultrasound exams were frequently performed in a subset of the animals (n = 96). All the statistical analyses for all experiments were performed with proc GLIMMIX and proc MIXED of SAS. Equine chorionic gonadotropin (eCG) treatment and body condition score (BCS) affected circulating progesterone in the diestrus. Cows in G2 had greater conception rates than cows in G4 (33,8% vs. 28,9%). In addition, in cows with lower BCS, eCG seems to be even more affective (G2 = 44,4% vs. G4 = 6,1%). In Experiment 2 (n = 26), the objective was to compare the effect of eCG the day of CIDR removal in animals with lower (2,0-2,5) or higher (3,0-3,5) BCS. Some variables such as corpus luteum (CL) volume, histology and circulating progesterone concentration in the diestrus were evaluated. Regardless of the body condition of the animals, eCG increased CL volume and circulating progesterone concentration in the diestrus. BCS negatively affected CL volume and circulating progesterone. There were no differences in large/small CL cell ratio, as well as CL blood flow between experimental groups. In Experiment 3, it was compared conception rate in dairy cows (n = 388) after using the same protocol G2 from Experiment 1 (Chapter I), with or without an ECP treatment at the time of CIDR (new or used) removal. Both ECP treatment and type of CIDR did not significantly affected conception rates. In Experiment 4 (n = 199), despite the fact that follicular diameter was increased in group GnRH 56h (17,8 mm) compared with GnRH 48h (16,5 mm); and of the delayed time of ovulation after CIDR removal (GnRH 56h = 75,3h; GnRH 48h = 79,8h), there were no differences in conception rates after delaying the GnRH treatment from 48h to 56h in cows inseminated 16h after GnRH. In Experiment 5 (n = 185), conception rate did not differ in animals that received GnRH 48h or 56h (at the time of TAI) after CIDR removal, indicating the possibility of using a protocol with only 3 handlings in high producing dairy cows.

L’amélioration de l’efficience alimentaire des animaux peut contribuer à un élevage plus durable par la réduction des ressources utilisées et des rejets associés. Les caractères qui déterminent l’efficience alimentaire des vaches laitières restent mal identifiés. Le projet se propose donc d’identifier les facteurs biologiques associés à la variabilité interindividuelle de l’efficience alimentaire des vaches laitières. La variation d’efficience alimentaire a été estimée avec l’ingéré résiduel, classiquement défini comme la variabilité résiduelle de l’énergie nette ingérée corrigée pour l’énergie nette du lait, l’entretien et les variations de réserves corporelles. Cet ingéré résiduel inclut par définition toutes les erreurs de mesure. Pour réduire ces erreurs, la note d’état corporel, qui classiquement se fait par notation visuelle, a été automatisée et de nombreux autres caractères candidats ont été mesurés fréquemment dans un environnement stable sur quasiment toute la lactation.La variabilité de l’ingéré résiduel ne représentait que 8% de la variabilité de l’ingéré mesuré, dont 58,9% étaient associés à de l’efficience et non de l’erreur. L’étude de la répétabilité de cet ingéré résiduel au cours de la lactation suggère d’éviter les 7 premières quinzaines au profit du milieu de lactation. Parmi tous les caractères mesurés, le comportement alimentaire, la température ruminale, la variation des réserves corporelles et l’activité expliquaient 58,9% de la variabilité de l’ingéré résiduel. Les effets de plusieurs de ces caractères semblent confondus. Leur lien de causalité av / Achieving higher feed efficiency of animals is expected to improve animal production sustainability through reduction of the used resources and of the associated emissions. The traits determining feed efficiency remain poorly understood. The present project aimed therefore at identifying the biological factors associated with feed efficiency differences in lactating dairy cows. Feed efficiency variation was estimated with the traditional residual intake, which was defined as the residual variability of net energy intake which is not explained by net energy required for lactation, maintenance and body reserves change. This residual intake includes by definition all measurement errors. To reduce these errors, body condition score, which is commonly measured visually, has been automated and several other candidate traits were measured frequently in a steady environment for almost whole lactation.Residual intake variability represented only 8% of intake variability in our study, among which only 58.9% were found to be associated with feed efficiency variability and not to errors. The repeatability analysis of the residual intake throughout the lactation suggested to avoid the 7 first lactation fortnights, and rather to focus on lactation middle. Among all measured traits, feeding behaviour, rumen temperature, body reserves change and activity explained 58.9% of residual intake variability. Many of these traits seemed confounded with others, which claimed for the need for further work to properly define their causal relationship with feed efficiency, especially focussing on di

Die Beziehungen zwischen der Reproduktionsleistung und der Körperkondition wurde in zwei Experimenten mit Awassi Schafen im Libanon untersucht. Im ersten Experiment wurden 72 Schafe in drei Altersklassen (Zutreter, primipare und multipare Mutterschafe), in zwei Körpergewichtsklassen (leichte, schwere) eingeteilt und jeweils zwei Fütterungsgruppen (ohne und mit Zufüterung) zugeordnet. Primipare und multipare Mutterschafe der Zufütterungsgruppe wiesen höhere Körperkondition, gemessen als BCS (p / The relationship between reproductive performances and body condition has been studied in 2 experiments using Awassi sheep in Lebanon. In the first exp., 72 experimental animals were grouped according to age (ewe lamb A, primiparous P, multiparous M), to body weight into small weight (SW) and large weight (LW), and kept under two management systems: traditional and improved (barley supplement). Primiparous and multiparous ewes showed a higher BCS (p

The alpaca is a small South American camelid (SAC) that is an important production animal in Peru, especially among the highly impoverished communities of the high Andes, and raised for its fiber and meat. Alpacas are highly reliant on the microbes within their digestive tracts to digest the plant material they consume; volatile fatty acids (VFAs) are released as a byproduct of this microbial fermentation and used as a major source of energy by the alpaca. To explore optimal parameters for alpaca microbiome analysis, performed 16S rRNA gene surveys on alpaca C1 and fecal samples that had been extracted using one of three different DNA extraction methods (PowerFecal® DNA Isolation Kit (MO BIO); ZR Fecal DNA MiniPrep™ (Zymo); and a non-commercial extraction method called salting out) and amplified using one of two different polymerase enzyme mixes (AccuPrime™ Pfx SuperMix and 5 PRIME HotMasterMix). We found that choice of polymerase enzyme had a profound effect on the recovered microbiome, with the majority of 5 PRIME-amplified fecal samples failing to amplify. Extraction method had an effect on the recovered microbiome of fecal samples (but not C1 samples), with samples extracted using the MO BIO kit and the salting out method recovering different communities. The Zymo extraction kit returned microbial communities comparable to each of the other extraction methods. These results suggested that the AccuPrime enzyme and either the MO BIO or Zymo kits were optimal for alpaca gut microbiome analysis. We also performed two 16S rRNA gene surveys, the first from alpacas fed either a grass hay (GH) or alfalfa hay (AH) diet, and the second a C1 survey of alpacas fed two-week periods of mixed grass hay plus one of four supplements. We discovered body site and diet effects on the microbiota of alpacas fed either the GH or AH diet, with samples grouping by general body site (C1, small intestine, and distal intestine) and diet. However, we found no significant effect on the C1 microbiome of alpacas administered grain supplements. To study how energy extraction related to the microbiome, we correlated OTUs from GH/AH-fed alpaca with C1 VFA abundances. We discovered no significant correlations, and a 16S survey of low body condition (LBC) and good body condition (GBC) alpacas showed no difference in C1 microbial communities. We concluded that the microbiota of the alpaca digestive tract follow trends seen in microbiome studies of ruminants, but found no evidence of a relationship between body condition, energy extraction, and the C1 microbiome in alpacas.

The aim of the thesis was to evaluate the data about body condition of cows and assess the relationship between changes of health status of the mammary gland, milk production and quality of cow´s milk. The monitoring took place in a selected company from October 2015 to September 2016 with the Czech spotted cattle. The body condition scoring was monitored within the herd, with the monthly evaluation of data, during the milking in the morning, together with the production performance control. The data values, received out of production performance control, were used for milk production performance (amount of milked milk, % fat, % protein, % lactose, SCC). Then the data about reproduction of the monitored herd were used, so as the order of lactation, date of the last calving and age. Total of 482 cows were monitored. During evaluation of the condition score, the average level of cows body condition was detected with value of 2, 18. Minimal body condition, during the monitored period, was 1.25, the maximum was 3.75. Correlation analysis of the relationship between the form and amount of the milked milk showed a negative correlation (-0.21). Furthermore the quality of milk was monitored. The amount of fat in milk, within the monitored herd, was 4.16% and 3.63% of protein. The fat was found to be the component, which the cow´s form had the effect on, with value: r = 0.14. The most affected component by the form was protein (0.28). A slight influence of pregnancy with Rf value = 0.06 arose too. Next evaluated indicator of milk quality was somatic cell count (SSC). The influence of the form, on SSC, was moderately significant (-0.05). The average somatic cell count, during the monitored period, was 287.75 thousand per milliliter. The prolificacy within the herd appears to be inconvenient. Within the population of the herd, the herd showed to be better at pregnancy rate after the first insemination (46.7%), however after all inseminations it proved to be weaker (44%). Subsequently the effect of three factors was evaluated: the day of pregnancy, the day of calving and the age in days at form. For dairy cows, at first lactation, there was found one significant influence the age, with the value of the correlation coefficient 0.23, while the cows at higher lactation showed to be influenced by all three of these factors. The dependence between the pregnancy day and the BCS is expressed as a negative (-0.06) but very weak. Higher absolute value of the correlation coefficient was observed between the age, in days, and BCS (-0.14). BCS value was directly proportional to days, since calving (0.16). This thesis was carried out with the support of the project Gaju 019/2016 / Z Nutrition and breeding technology as a way to animal welfare and the product quality.

Investigou-se o desempenho reprodutivo de novilhas e vacas de corte submetidas a protocolos de sincronização de estros para a inseminação artificial e a associação entre marcadores moleculares e desempenho reprodutivo. Exp.1 avaliou-se a antecipação da aplicação da PGF2a em programa de IATF com implante de progesterona em 306 vacas Angus, com cria ao pé. A antecipação da aplicação da PGF2a afetou a taxa de concepção à IATF e prenhez final (P<0,05), respectivamente de 60,9% e 89,1% quando comparados a PGF2a na retirada do dispositivo, respectivamente de 49,3% e 76,7%. Exp.2 avaliaram-se os efeitos do GnRH e da manifestação de estro sobre o desempenho reprodutivo em 197 vacas Angus submetidas à IATF. A manifestação de estro antes da IATF influenciou a taxa de prenhez à IATF (TxPIATF) e prenhez final, respectivamente de 46,6%, 78,6% (C/estro) e 33,0%, 60,6% (S/estro) (P<0,05). O GnRH no momento da IATF resultou em menor taxa de prenhez à IATF, 32,3%, comparado a ausência de GnRH 48,0% (P<0,05), mas não afetou a prenhez final, respectivamente de 69,7% e 70,4%. Houve interação entre estro e GnRH. Vacas C/estro-C/GnRH tiveram 31,4% de prenhez à IATF contra vacas C/estro- S/GnRH com 61,5% (P<0,05). Nas vacas sem estro, o GnRH não apresentou efeito (P>0,05) na TxPIATF (32,6% e 33,3%). O escore de condição corporal (ECC) afetou a taxa de manifestação de estro e a TxPIATF, com superioridade (P<0,05) para vacas > de 3,0. Exp.3 compararam-se os efeitos de diferentes protocolos para a IATF com o acasalamento por touros (Controle) sobre o desempenho reprodutivo de 249 vacas Angus. Formou-se 5 grupos: Controle; Crestar 2º uso; OvSynch; Primer 1ºuso e Primer 2ºuso. A IATF dos animais foi realizada 27 dias e 38 dias após o inicio da estação do grupo controle. Sete dias após a IATF iniciou o repasse com touros. A estação de acasalamento (EA) foi de 91 dias para o grupo controle e 64 e 53 dias para os grupos IATF. A taxa de prenhez ao final da EA não se diferenciou entre os grupos 83,9%. As perdas reprodutivas entre o diagnóstico de gestação e o nascimento foram de 10,5%, sem diferenças entre grupos. O ECC de fêmeas que emprenharam no grupo controle foi diferente do ECC de fêmeas vazias, mas não se diferenciou nos animais da IATF. Exp.4 avaliaram-se protocolos de inseminação sobre o índice reprodutivo em 249 novilhas Britânicas e cruzas, acasaladas aos 14 e 27 meses. Novilhas de 14 e 27 meses foram submetidas aos tratamentos Crestar ou inseminação artificial (IA) por 7 dias, seguida por mais 5 dias após PGF2a (grupo PGF2a) Novilhas de 27 meses também foram submetidas ao OvSynch. Foram avaliados o peso vivo, ECC, escore de trato reprodutivo (ETR) ao início da estação reprodutiva. Os tratamentos OvSynch e Crestar tiveram 100% dos animais inseminados (IATF), enquanto os grupos IA com PGF2a aos 14 e 27 meses tiveram, respectivamente 21,9% e 43,5%. Não houve diferença nas taxas de concepção entre tratamentos e idades (P>0,05), com valores respectivos de 46,5%, 56,3%, 64,7% para Crestar, OvSynch, PGF2a e de 44,4% e 57,1%, para 14 e 27 meses. A taxa de prenhez à IA(TF) foi de 46,5%, 56,3%, 23,4% para Crestar, OvSynch, PGF2a, com superioridade (P<0,05) a favor do Crestar e OvSynch. A taxa de prenhez à IA(TF) foi de 18,6% e 41,3% (P<0,01) para idades 14 e 27 meses. A taxa de prenhez final, após o repasse com touros, foi superior a 90% em todos os grupos (P<0,05). O ETR influenciou a taxa de prenhez após a inseminação. Exp.5 e 6 buscou-se uma associação entre a resposta reprodutiva e marcadores moleculares ligados aos genes do receptor para IGF-1, LH , Leptina, receptores do FSH e LH. Foram utilizados dados de 249 novilhas (Exp4.) e 249 vacas (Exp.3). Nas novilhas a prenhez à inseminação e a prenhez final foram de 41,0% e 91,6%. Nas novilhas não foram encontradas associações entre marcadores e reprodução. No rebanho das vacas a taxa de natalidade no ano subseqüente foi de 75,5%, sem diferenças entre tratamentos, idade e escore ovariano. O ECC influenciou a taxa de natalidade, respectivamente de 55,6%, 75,8% e 82,4% (P<0,05) para os animais com ECC menor que 2,5; 2,5 a 2,9; maior ou igual a 3,0 ao do inicio EA. Vacas homozigóticas no marcador AFZ-1 apresentaram 84,4% de natalidade em comparação as heterozigóticas com 71,5% (P<0,05). A presença do alelo*161 nomarcador HEL5 resultou em 33,3% de natalidade, contra 76,5% em vacas sem esse alelo (P<0,05). Os experimentos evidenciaram que a antecipação da aplicação da PGF2a resultou em aumento da taxa de prenhez à IATF. O ECC mostrou-se como importante preditor do desempenho reprodutivo em vacas de corte. O uso do GnRH concomitante à IATF em vacas com manifestação de estro induzido com benzoato resultou em menor resposta reprodutiva à IATF. A IATF proporcionou aumento nas taxas de inseminação em novilhas, especialmente nas submetidas ao acasalamento 14 meses. O escore de trato reprodutivo ao início da estação de acasalamento influenciou a precocidade de concepção das novilhas. O atraso da realização da IATF após o início da EA não afetou a taxa de prenhez final de vacas de cria quando comparado ao acasalamento por touros. Marcadores moleculares apresentaram associação com o desempenho reprodutivo de bovinos. / Were investigated the reproductive performance of beef heifers and cows submitted to different estrus synchronization protocols for artificial insemination and the association between molecular markers and reproductive performance. Trial.1 The anticipation of the application of PGF2a in TAI program with implantation of progesterone in 306 nursing Angus cows was evaluated. Anticipating the application of PGF2a affected (P <0.05) conception rate to TAI and final pregnancy, respectively 60.9% and 89.1% when compared to PGF2a in the removal of the device, respectively 49.3% and 76.7%. Trial.2 The effects of GnRH and oestrus on reproductive performance in 197 Angus cows subjected to TAI It were evaluated. The expression of oestrus before TAI influenced the pregnancy rate to TAI (TxPTAI) and final pregnancy (P<0.05), respectively 46.6%, 78.6% (oestrus) and 33.0%, 60.6% (No/oestrus). GnRH at the time of TAI resulted in lower pregnancy rate to TAI (32.3%) compared to the absence of GnRH (48.0%) (P<0.05) but did not affect the final pregnancy, respectively 69, 7% and 70.4%. There was interaction between GnRH and oestrus. Cows with oestrus and GnRH had 31.4% pregnancy for TAI cows against with oestrus without GnRH with 61.5% (P <0.05). In cows without oestrus, GnRH had no effect (P> 0.05) TxPTAI (32.6% and 33.3%). The body condition score (BCS) affected the rate of oestrus and TxPTAI, with higher (P <0.05) for cows > than 3.0. Trial.3 The effects of different protocols for TAI with mating by bulls (control) on the reproductive performance of 249 Angus cows were compared. It was formed five groups: Control; Crestar 2nd use; OvSynch; Primer new and Primer 2nd use. The TAI was performed 27 days and 38 days after the start breeding season in the control group. Seven days after TAI was realized the clean-up bulls. The mating season (MS) was 91 days for the control group and 64 and 53 days for TAI groups. Pregnancy rate at the end of MS did not differ between groups (83.9%). Reproductive failure between diagnosis of pregnancy and birth were 10.5%, without differences between groups. The BCS to pregnant cows in the control group differed from open cows, but it was not different in cows submitted to TAI. Trial.4 Different protocols to insemination on reproduction in 249 British and crossbred heifers, bred at 14 and 27 months were evaluated. Heifers to 14 and 27 months were treated Crestar or artificial insemination (AI) for 7 days, followed by more than 5 days after PGF2a (PGF2a group) Heifers 27 months were also submitted to OvSynch. We evaluated body weight, BCS, reproductive tract score (RTS) to the beginning of the breeding season. Treatments OvSynch and Crestar had 100% of the animals inseminated (TAI), while groups with PGF2a IA at 14 and 27 months were respectively 21.9% and 43.5%. There was no difference in conception rates between treatment and age (P>0.05), with respective values of 46.5%, 56.3%, 64.7% for Crestar, OvSynch, PGF2a, and 44.4% and 57.1% for 14 and 27 months. Pregnancy rate to AI (TAI) was 46.5%, 56.3%, 23.4% for Crestar, OvSynch, PGF2a, with higher (P <0.05) in favor of Crestar and OvSynch. Pregnancy rate to AI (TAI) was 18.6% and 41.3% (P <0.01) for ages 14 and 27 months. The final pregnancy rate after clean-up bulls was superior to 90% in all groups (P<0.05). The RTS influenced the pregnancy rate after insemination. Trial.5 and 6 we looking for an association between the reproductive response and molecular markers linked to genes for IGF-1 receptor, LH , Leptin, FSH and LH receptors. We used data from 249 heifers (Trial4.) and 249 cows (Trial.3). Pregnancy in heifers at insemination and final pregnancy were 41.0% and 91.6%. No associations were found between markers and reproduction in heifers. In the cow`s herd the birth rate in subsequent years was 75.5%, with no differences between treatments, age and ovarian score. The BCS has influenced the birth rate, respectively 55.6%, 75.8% and 82.4% (P <0.05) for animals with BCS less than 2.5, 2.5 to 2.9; greater than or equal to 3.0 to the beginning of the MS. Cows in homozygous marker AFZ-1 showed 84.4% of the birth rate compared with 71.5% (P <0.05) in heterozygous cows. The presence of allele*161 to HEL5 marker resulted in 33.3% of birth rate vs. 76.5% in cows without this allele (P<0.05). The experiments showed that the anticipation of the implementation of PGF2a resulted in increased pregnancy rate to TAI. BCS has proven to be an important predictor of reproductive performance in beef cows. The use of GnRH in cows with the oestrus induced with benzoate showed worse reproductive response to TAI. The TAI has provided increased rates of insemination in heifers, especially in heifers submitted to matting by 14 months. The reproductive tract score at the beginning of the breeding season influenced the speed of conception in heifers. The delay of the realization of TAI after the onset of MS did not affect the final pregnancy rate of beef cows when compared to breeding only by bulls. Molecular markers were associated with the reproductive performance of cattle.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The present study was developed with the objective of evaluate if the frequency of roughage and supplement supply and/or animal category affect performance and behavior of feedlot cattle. Sixteen heifers and sixteen cows were used, with average initial age of 20 and 66 months and average initial weight of 338 and 462 kg, respectively. The frequencies of roughage and supplement supply were: 2 V/C roughage and supplement 2 times per day; 1 V/C roughage and supplement 1 time per day; 1 V/2 C roughage 1 time per day and supplement 2 times per day; 1 V/3 C roughage 1 time per day and supplement 3 times per day. Each food supply was offered to cows and heifers. The supplied diet was composed by 60% of maize silage and 40% of concentrate, on dry matter base (DM). The process of obtaining performance parameters was by animal weighting and attribution of body condition, weighting of the supplied food and it s respective orts, chemical analysis of diet ingredients and orts. Behavior parameters were obtained by register of animal activities at each 5 minutes, beyond counting chews per ruminated bolus and it s duration. The complete randomized experimental design was used, with a 4 x 2 factorial arrangement. No significant interaction was observed (P>.05) between supply frequencies and animal category for performance variables. For ingestive behavior, was observed interaction between supply and animal category for rumination (RT) and idle (IDT) times, efficiencies of dry matter rumination (EDMR) and neutral detergent fiber rumination (ENDFR), number of daily bolus and daily time of chews (DTC). Supply frequencies did not influence (P>.05) average daily weight gain (ADWG). Dry matter intake (DMI) per animal was superior for animal of 1 V/2 C or 1 V/3 C treatments. The DMI and digestible energy intake per animal and per metabolic size were higher for cows, however ADWG was similar (1.330 vs. 1.378, respectively), resulting on worst food conversion for cows in relation to heifers (9.4 vs. 7.4 kg, respectively). Heifers showed higher (P<.05) IDT and DTC when compared with cows that received food once in a day. Time of food intake (TFI) did not vary (P>.05) with supply frequencies. Ingestion rate (IR) was higher (P<.05) for animals that received 1 V/3 C, and did not differ from the ones that received 1 V/2 C in relation to 1 V/C and 2 V/C supply frequencies (2.89; 2.72; 2.43 and 2.48 kg of DM/hour of intake, respectively). Cows were higher for TFI and IR in relation to heifers (4.38 vs. 4.09 hours, 2.91 vs. 2.35 kg of DM/hour of intake, respectively). The frequencies supply of one, two or three times per day stimulates animals to intensify ingestion on the moment of the supply, but this don t alter time of food intake during the day and animals weight gain. / O presente estudo foi desenvolvido com o objetivo de avaliar se a freqüência do fornecimento do volumoso e concentrado e/ou a categoria animal afetam o desempenho e o comportamento de bovinos confinados. Foram utilizadas 16 novilhas e 16 vacas, com idade média inicial de 20 e 66 meses e peso médio inicial de 338 e 432 kg, respectivamente. As freqüências do fornecimento do volumoso e concentrado foram as seguintes: 2 V/C volumoso e concentrado 2 vezes ao dia; 1 V/C volumoso e concentrado 1 vez ao dia; 1 V/2 C volumoso 1 vez ao dia e o concentrado 2 vezes ao dia; 1 V/3 C volumoso 1 vez ao dia e o concentrado 3 vezes ao dia. Cada fornecimento alimentar foi ofertado nas categorias vaca e novilha. A dieta fornecida aos animais foi composta de 60% de silagem de milho e 40% de concentrado com base na matéria seca (MS). A obtenção das variáveis de desempenho ocorreu pela pesagem e atribuição de escore corporal aos animais, pesagem do alimento fornecido e respectivas sobras, análise bromatológica dos ingredientes da dieta e das sobras. As variáveis de comportamento foram avaliadas através do registro de atividades dos animais a cada 5 minutos, além da contagem de mastigações por bolo ruminado e sua duração. O delineamento experimental adotado foi inteiramente casualizado em arranjo fatorial 4 x 2 (fornecimentos x categoria animal). Não houve interação significativa (P>0,05) entre freqüência de fornecimento e categoria animal para as variáveis de desempenho. Para o comportamento ingestivo, foi observada interação entre o fornecimento e a categoria animal para o tempo de ruminação (TR) e ócio (TO), eficiência de ruminação da matéria seca (ERMS) e da fibra detergente neutro (ERFDN), número de bolos diário e tempo de mastigação diário (TMD). As freqüências do fornecimento não influenciaram (P>0,05) o ganho de peso médio diário (GMD). O consumo de matéria seca (CMS) por animal foi superior para os animais alimentados 1 V/2 C ou 1 V/3 C. O CMS e o consumo de energia digestível por animal e por tamanho metabólico foram superiores para as vacas em relação às novilhas, porém, o GMD foi semelhante (1,330 vs 1,378 kg, respectivamente), resultando em pior conversão alimentar (9,4 vs 7,4 kg, respectivamente). As novilhas apresentaram maiores (P<0,05) TO e TMD em relação às vacas quando receberam a alimentação uma vez ao dia. O tempo de consumo de alimento (TCA) não teve variação (P>0,05) conforme a freqüência do fornecimento da dieta. A taxa de ingestão (TI) foi superior (P<0,05) para os animais que receberam 1 V/3 C, e esta não diferiu dos que receberam 1 V/2 C em relação aos fornecimentos de 1 V/C e 2 V/C (2,89; 2,72; 2,43 e 2,48 kg de MS/hora de consumo, respectivamente). As vacas permaneceram mais TCA e apresentaram maiores TI em comparação às novilhas (4,38 vs 4,09 horas; 2,91 vs 2,35 kg de MS/hora de consumo, respectivamente). A freqüência do fornecimento do alimento aos animais em uma, duas ou três vezes ao dia estimula estes a intensificar a ingestão no momento do fornecimento, mas isso não altera o tempo de ingestão do alimento ao longo do dia e o ganho de peso dos animais.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Feeding behavior, forage intake by beef heifers, the pasture structure in two phenological stages of annual ryegrass (Lolium multiflorum): pre-flowering and flowering with heifers subjected to different feed systems: heifers exclusively on pasture or receiving corn grain (0.78% of body weight) or extruded fat (0.2% of body weight) as a supplement was studied. The experimental design was completely randomized in a factorial arrangement 3 x 2 (three supplements x two phenological stages of Italian ryegrass). The behavioral assessments were made by visual observation in four continuous 14 hour periods. Total DM and pastures intake were similar in both phenological stages. DM intake from pasture was higher for heifers consuming only ryegrass, intermediate for heifers that received fat, and lower when the supplement used was corn grain. Average daily gain of heifers was similar, regardless of the supplement received and the phenological stage of the ryegrass. The body condition score of heifers was similar in evaluations at pre-flowering and flowering stage of ryegrass. The heifers receiving corn grain had higher body condition score. The supply of corn grain caused a stocking rate 18% above other supplements tested. Grazing and ruminating time did not differ with the advance of the ryegrass cycle. Idle time was reduced from 312.22 to 228.68 minutes / day in the pre-flowering and flowering stage. The diurnal grazing, rumination and idle time were similar among heifers receiving different treatments. / Foram estudados o comportamento ingestivo, o consumo de forragem por novilhas de corte e a estrutura da pastagem em dois estádios de desenvolvimento do azevém (Lolium multiflorum Lam.): pré-florescimento e florescimento com bezerras submetidas à diferentes sistemas alimentares : novilhas exclusivamente em pastejo ou recebendo grão de milho (0,78% de peso corporal de grão de milho) ou gordura extrusada como suplemento (0,2% de peso corporal de gordura extrusada. O delineamento experimental foi o inteiramente casualizado, com arranjo fatorial 3 x 2 (três suplementos x dois estádios fenológicos do azevém). As avaliações de comportamento foram feitas por meio de observação visual, em quatro períodos contínuos de 14 horas. As ingestões de MS total e do pasto foram semelhantes nos dois estádios fenológicos. A ingestão de MS do pasto foi maior para as novilhas exclusivamente em pastagem de azevém, intermediária para as novilhas que recebiam gordura, e inferior quando o suplemento utilizado foi o milho. O ganho médio diário das novilhas foi semelhante, independente do suplemento recebido e do estádio fenológico do azevém. O escore de condição corporal das novilhas foi semelhante nas avaliações no estádio pré-florescimento e florescimento do azevém. As novilhas que receberam milho apresentaram escore de condição corporal superior. O fornecimento de milho ocasionou taxa de lotação 18% superior aos demais suplementos testados. Os tempos de pastejo e ruminação não diferiram com o avanço do ciclo do azevém. O tempo de ócio foi reduzido de 312,22 para 228,68 minutos/dia do pré-florescimento para o florescimento. O tempo diurno de pastejo, ruminação e de ócio foi semelhante entre as novilhas que recebiam os diferentes suplementos.

Investigou-se o desempenho reprodutivo de novilhas e vacas de corte submetidas a protocolos de sincronização de estros para a inseminação artificial e a associação entre marcadores moleculares e desempenho reprodutivo. Exp.1 avaliou-se a antecipação da aplicação da PGF2a em programa de IATF com implante de progesterona em 306 vacas Angus, com cria ao pé. A antecipação da aplicação da PGF2a afetou a taxa de concepção à IATF e prenhez final (P<0,05), respectivamente de 60,9% e 89,1% quando comparados a PGF2a na retirada do dispositivo, respectivamente de 49,3% e 76,7%. Exp.2 avaliaram-se os efeitos do GnRH e da manifestação de estro sobre o desempenho reprodutivo em 197 vacas Angus submetidas à IATF. A manifestação de estro antes da IATF influenciou a taxa de prenhez à IATF (TxPIATF) e prenhez final, respectivamente de 46,6%, 78,6% (C/estro) e 33,0%, 60,6% (S/estro) (P<0,05). O GnRH no momento da IATF resultou em menor taxa de prenhez à IATF, 32,3%, comparado a ausência de GnRH 48,0% (P<0,05), mas não afetou a prenhez final, respectivamente de 69,7% e 70,4%. Houve interação entre estro e GnRH. Vacas C/estro-C/GnRH tiveram 31,4% de prenhez à IATF contra vacas C/estro- S/GnRH com 61,5% (P<0,05). Nas vacas sem estro, o GnRH não apresentou efeito (P>0,05) na TxPIATF (32,6% e 33,3%). O escore de condição corporal (ECC) afetou a taxa de manifestação de estro e a TxPIATF, com superioridade (P<0,05) para vacas > de 3,0. Exp.3 compararam-se os efeitos de diferentes protocolos para a IATF com o acasalamento por touros (Controle) sobre o desempenho reprodutivo de 249 vacas Angus. Formou-se 5 grupos: Controle; Crestar 2º uso; OvSynch; Primer 1ºuso e Primer 2ºuso. A IATF dos animais foi realizada 27 dias e 38 dias após o inicio da estação do grupo controle. Sete dias após a IATF iniciou o repasse com touros. A estação de acasalamento (EA) foi de 91 dias para o grupo controle e 64 e 53 dias para os grupos IATF. A taxa de prenhez ao final da EA não se diferenciou entre os grupos 83,9%. As perdas reprodutivas entre o diagnóstico de gestação e o nascimento foram de 10,5%, sem diferenças entre grupos. O ECC de fêmeas que emprenharam no grupo controle foi diferente do ECC de fêmeas vazias, mas não se diferenciou nos animais da IATF. Exp.4 avaliaram-se protocolos de inseminação sobre o índice reprodutivo em 249 novilhas Britânicas e cruzas, acasaladas aos 14 e 27 meses. Novilhas de 14 e 27 meses foram submetidas aos tratamentos Crestar ou inseminação artificial (IA) por 7 dias, seguida por mais 5 dias após PGF2a (grupo PGF2a) Novilhas de 27 meses também foram submetidas ao OvSynch. Foram avaliados o peso vivo, ECC, escore de trato reprodutivo (ETR) ao início da estação reprodutiva. Os tratamentos OvSynch e Crestar tiveram 100% dos animais inseminados (IATF), enquanto os grupos IA com PGF2a aos 14 e 27 meses tiveram, respectivamente 21,9% e 43,5%. Não houve diferença nas taxas de concepção entre tratamentos e idades (P>0,05), com valores respectivos de 46,5%, 56,3%, 64,7% para Crestar, OvSynch, PGF2a e de 44,4% e 57,1%, para 14 e 27 meses. A taxa de prenhez à IA(TF) foi de 46,5%, 56,3%, 23,4% para Crestar, OvSynch, PGF2a, com superioridade (P<0,05) a favor do Crestar e OvSynch. A taxa de prenhez à IA(TF) foi de 18,6% e 41,3% (P<0,01) para idades 14 e 27 meses. A taxa de prenhez final, após o repasse com touros, foi superior a 90% em todos os grupos (P<0,05). O ETR influenciou a taxa de prenhez após a inseminação. Exp.5 e 6 buscou-se uma associação entre a resposta reprodutiva e marcadores moleculares ligados aos genes do receptor para IGF-1, LH , Leptina, receptores do FSH e LH. Foram utilizados dados de 249 novilhas (Exp4.) e 249 vacas (Exp.3). Nas novilhas a prenhez à inseminação e a prenhez final foram de 41,0% e 91,6%. Nas novilhas não foram encontradas associações entre marcadores e reprodução. No rebanho das vacas a taxa de natalidade no ano subseqüente foi de 75,5%, sem diferenças entre tratamentos, idade e escore ovariano. O ECC influenciou a taxa de natalidade, respectivamente de 55,6%, 75,8% e 82,4% (P<0,05) para os animais com ECC menor que 2,5; 2,5 a 2,9; maior ou igual a 3,0 ao do inicio EA. Vacas homozigóticas no marcador AFZ-1 apresentaram 84,4% de natalidade em comparação as heterozigóticas com 71,5% (P<0,05). A presença do alelo*161 nomarcador HEL5 resultou em 33,3% de natalidade, contra 76,5% em vacas sem esse alelo (P<0,05). Os experimentos evidenciaram que a antecipação da aplicação da PGF2a resultou em aumento da taxa de prenhez à IATF. O ECC mostrou-se como importante preditor do desempenho reprodutivo em vacas de corte. O uso do GnRH concomitante à IATF em vacas com manifestação de estro induzido com benzoato resultou em menor resposta reprodutiva à IATF. A IATF proporcionou aumento nas taxas de inseminação em novilhas, especialmente nas submetidas ao acasalamento 14 meses. O escore de trato reprodutivo ao início da estação de acasalamento influenciou a precocidade de concepção das novilhas. O atraso da realização da IATF após o início da EA não afetou a taxa de prenhez final de vacas de cria quando comparado ao acasalamento por touros. Marcadores moleculares apresentaram associação com o desempenho reprodutivo de bovinos. / Were investigated the reproductive performance of beef heifers and cows submitted to different estrus synchronization protocols for artificial insemination and the association between molecular markers and reproductive performance. Trial.1 The anticipation of the application of PGF2a in TAI program with implantation of progesterone in 306 nursing Angus cows was evaluated. Anticipating the application of PGF2a affected (P <0.05) conception rate to TAI and final pregnancy, respectively 60.9% and 89.1% when compared to PGF2a in the removal of the device, respectively 49.3% and 76.7%. Trial.2 The effects of GnRH and oestrus on reproductive performance in 197 Angus cows subjected to TAI It were evaluated. The expression of oestrus before TAI influenced the pregnancy rate to TAI (TxPTAI) and final pregnancy (P<0.05), respectively 46.6%, 78.6% (oestrus) and 33.0%, 60.6% (No/oestrus). GnRH at the time of TAI resulted in lower pregnancy rate to TAI (32.3%) compared to the absence of GnRH (48.0%) (P<0.05) but did not affect the final pregnancy, respectively 69, 7% and 70.4%. There was interaction between GnRH and oestrus. Cows with oestrus and GnRH had 31.4% pregnancy for TAI cows against with oestrus without GnRH with 61.5% (P <0.05). In cows without oestrus, GnRH had no effect (P> 0.05) TxPTAI (32.6% and 33.3%). The body condition score (BCS) affected the rate of oestrus and TxPTAI, with higher (P <0.05) for cows > than 3.0. Trial.3 The effects of different protocols for TAI with mating by bulls (control) on the reproductive performance of 249 Angus cows were compared. It was formed five groups: Control; Crestar 2nd use; OvSynch; Primer new and Primer 2nd use. The TAI was performed 27 days and 38 days after the start breeding season in the control group. Seven days after TAI was realized the clean-up bulls. The mating season (MS) was 91 days for the control group and 64 and 53 days for TAI groups. Pregnancy rate at the end of MS did not differ between groups (83.9%). Reproductive failure between diagnosis of pregnancy and birth were 10.5%, without differences between groups. The BCS to pregnant cows in the control group differed from open cows, but it was not different in cows submitted to TAI. Trial.4 Different protocols to insemination on reproduction in 249 British and crossbred heifers, bred at 14 and 27 months were evaluated. Heifers to 14 and 27 months were treated Crestar or artificial insemination (AI) for 7 days, followed by more than 5 days after PGF2a (PGF2a group) Heifers 27 months were also submitted to OvSynch. We evaluated body weight, BCS, reproductive tract score (RTS) to the beginning of the breeding season. Treatments OvSynch and Crestar had 100% of the animals inseminated (TAI), while groups with PGF2a IA at 14 and 27 months were respectively 21.9% and 43.5%. There was no difference in conception rates between treatment and age (P>0.05), with respective values of 46.5%, 56.3%, 64.7% for Crestar, OvSynch, PGF2a, and 44.4% and 57.1% for 14 and 27 months. Pregnancy rate to AI (TAI) was 46.5%, 56.3%, 23.4% for Crestar, OvSynch, PGF2a, with higher (P <0.05) in favor of Crestar and OvSynch. Pregnancy rate to AI (TAI) was 18.6% and 41.3% (P <0.01) for ages 14 and 27 months. The final pregnancy rate after clean-up bulls was superior to 90% in all groups (P<0.05). The RTS influenced the pregnancy rate after insemination. Trial.5 and 6 we looking for an association between the reproductive response and molecular markers linked to genes for IGF-1 receptor, LH , Leptin, FSH and LH receptors. We used data from 249 heifers (Trial4.) and 249 cows (Trial.3). Pregnancy in heifers at insemination and final pregnancy were 41.0% and 91.6%. No associations were found between markers and reproduction in heifers. In the cow`s herd the birth rate in subsequent years was 75.5%, with no differences between treatments, age and ovarian score. The BCS has influenced the birth rate, respectively 55.6%, 75.8% and 82.4% (P <0.05) for animals with BCS less than 2.5, 2.5 to 2.9; greater than or equal to 3.0 to the beginning of the MS. Cows in homozygous marker AFZ-1 showed 84.4% of the birth rate compared with 71.5% (P <0.05) in heterozygous cows. The presence of allele*161 to HEL5 marker resulted in 33.3% of birth rate vs. 76.5% in cows without this allele (P<0.05). The experiments showed that the anticipation of the implementation of PGF2a resulted in increased pregnancy rate to TAI. BCS has proven to be an important predictor of reproductive performance in beef cows. The use of GnRH in cows with the oestrus induced with benzoate showed worse reproductive response to TAI. The TAI has provided increased rates of insemination in heifers, especially in heifers submitted to matting by 14 months. The reproductive tract score at the beginning of the breeding season influenced the speed of conception in heifers. The delay of the realization of TAI after the onset of MS did not affect the final pregnancy rate of beef cows when compared to breeding only by bulls. Molecular markers were associated with the reproductive performance of cattle.